THE PRIMARY AIM OF THE PROPOSED INVESTIGATION IS TO CONTINUE TO DEVELOP AND INTEGRATE THE NONSPHERICAL SNOW AND MELTING PARTICLE MODELS AND THEN TEST THESE PARTICLE MODELS FOR CONSISTENCY WITH AIRBORNE AND GPM RADAR-RADIOMETER OBSERVATIONS AS WELL AS INDEPENDENT VALIDATION DATA. TO THIS END WE PROPOSE TO:-EXTEND THE CURRENT DATABASE OF NONSPHERICAL SNOW PARTICLES TO INCLUDE LARGER PARTICLE SIZES AS WELL AS RIMED PARTICLES; THEN CALCULATE THE SINGLE-SCATTERING PROPERTIES OF THESE PARTICLES.-SIMULATE THE MELTING OF A SUBSET OF PARTICLES IN THE SNOW PARTICLE DATABASE AND COMPUTE THEIR SINGLE-SCATTERING PROPERTIES AND ALSO GENERALIZE THE 1-D THERMODYNAMIC MODEL OF THE MELTING LAYER BY ADDING PARTICLE AGGREGATION.-INTRODUCE THE BULK SINGLE-SCATTERING PROPERTIES OF THE SNOW AND MELTING PARTICLES INTO A COMBINED ALGORITHM FRAMEWORK SUITABLE FOR TESTING THE RADIATIVE CONSISTENCY OF THE PARTICLE PROPERTIES WITH SIMULTANEOUS AIRBORNE RADAR AND RADIOMETER OBSERVATIONS FROM FIELD CAMPAIGNS AND USE IN SITU PARTICLE PROBE DATA TO INDEPENDENTLY CHECK RADIATIVELY-CONSISTENT PARTICLE DISTRIBUTIONS.-EVALUATE THE PARTICLE MODELS IN GPM COMBINED RADAR-RADIOMETER ALGORITHM APPLICATIONS AND USE AVAILABLE GROUND OBSERVATIONS TO PERFORM A PRELIMINARY VALIDATION OF ESTIMATES.